This project is concerned with the conduction of action potentials in peripheral nerve fibers in normal and damaged nerves. One study has been to develop and apply accurate methods for determining conduction velocity in short segments of peripheral nerves and spinal roots. This has resulted in the selection of spike-triggered averaging to obtain incremental latency in adjacent sets of tripolar nerve cuff electrodes, and the finding that there is no significant slowing of myelinated afferents from sciatic nerve to dorsal root in the cat. A second study has been to apply this technique to the study of electrically evoked nerve potentials in chronically implanted animals during the periods of atrophy and regeneration in compressed peripheral nerves. This has permitted a detailed examination of the effects of and time course of recovery from experimentally induced compression neuropathy. The presence of a chronic constriction slows regeneration distally and that even after the distal segment has reached an almost normal conduction velocity, there may continue to be considerable slowing in the region of the constriction. One unexpected result is that smaller myelinated fibers in a proximal stump of crushed nerve (Group II caliber) appear to regenerate distal projections earlier than the largest (Group I) fibers.